Did the picture actually come first? Just there are a few important differences between the two that kind of give me the impression that those lot are actually just attempting to act-out what is going on in the picture.

Judging from the shape of the hips I'd also say that the Pinkie Cosplayer is also a girl so... this would give some much needed context on the OP whilst making it kinda weird in another. (Still, not like we haven't seen cosplayers do stranger stuff.)